1. Technical Field
The present invention relates to an image reading apparatus (image scanner) that optically reads a document.
2. Related Art
An apparatus in which multiple line sensors that respectively image different color components individually (for example, red, blue, and green) are disposed approximately parallel to one another in the main scanning direction, and a document is read while moving the positional relationship between the multiple line sensors and the document relative to each other in the sub scanning direction, which is orthogonal to the main scanning direction, is known as a past example of an image reading apparatus (see JP-A-1-97055 and JP-A-7-23181). With such an image reading apparatus, scan data of each color component imaged by the multiple line sensors at the same timing is thus data in which regions of the document that are skewed relative to each other in the sub scanning direction have been imaged. The positional skew in the sub scanning direction of the scan data for the respective color components is then adjusted in accordance with an offset amount based on the distance between the multiple line sensors, and image data expressing the original document is then generated based on the adjusted scan data.
However, in the past, there has been a problem in that if the image formation magnification of the document as formed upon the line sensors deviates from the design value for some reason (for example, individual differences in the optical system, deterioration due to age, and so on), positional skew in the sub scanning direction caused by the amount of the deviation in the image formation magnification will appear in the post-adjustment scan data. Positional skew in the sub scanning direction in the post-adjustment scan data is a cause of color skew in the image data that expresses the document.